Form and method and apparatus for making a form

ABSTRACT

A concrete form having a tubular body formed from a flexile strip wound helically in successive passes to define a wall of the form. The adjacent edges of the strip being releasably engaged with one another to exhibit axial separation of the strip.

This application claims priority from U.S. Provisional PatentApplication No. 60/831,226 filed on Jul. 17, 2006.

FIELD OF THE INVENTION

The present invention relates to forms for moulding material and tomethods and apparatus of creating such form-s.

SUMMARY OF THE INVENTION

Forms are used in a variety of applications to provide temporarycontainment for mouldable materials. A typical application of such formis in the pouring of concrete where it is necessary to hold the concretein the desired shape until it has set. A commonly used form is acylindrical tube that is used to establish pillars or piers to supportadditional structure. Typically, these tubes, commonly known by thetrademark “Sonotube” are formed from layers of paper material that arehelically wound and glued to one another during forming to produce arigid structure. The tubes have sufficient strength to support concreteand, upon setting, the layers of the tube can be removed to expose theconcrete.

Such tubes are widely used and are available from building supply storesin a variety of sizes. The sizes may range from 6 inches to 12 inchesand the tubes are stored in a length that permits transportation,typically 20 feet. However, the storage of such tubes is difficult sincethey cannot be easily stacked one on top of the other due to theircircular nature and is also in efficient as one tube occupies a largevolume. Although some efficiency can be realized by nesting a smallerdiameter tube within a larger one for transportation, this isimpractical in the environment of a building supply store and also timeconsuming to pack the nested tubes.

There is therefore the need for a form that can offer efficiencies forstorage and transportation without impairing the utility of the tube.

In general terms, the present invention provides a form that ishelically wound from a flexible strip. The strip has a groove formedadjacent one edge and a complementary tongue formed on the oppositeedge. The tongue and groove are dimensioned so as to be a snap fit toretain successive passes of the strip in forming a helical tube.

Preferably, the groove is undercut and the tongue has an enlarged headto enhance the retention within the groove. As a further preference, alocking key may be provided to expand the tongue after insertion andthereby enhance the retention of the tongue within the groove.

By providing a form of the structure described above, it is simplynecessary to store rolls of strip that can then be deployed to form acylinder of the required dimension and length.

In a further aspect of the invention, a forming machine is provided withan expandable mandrel to guide a strip in a helical path. A pinch rolleris provided to force a tongue into an adjacent groove and as a furtherpreference, a key strip may be pressed into the tongue subsequent to thepinch roller.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described by way of exampleonly with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of a cylindrical form

FIG. 2 is a view on the line II of FIG. 1.

FIG. 3 is an enlarged view of a section of a strip used to form the tubeshown in FIGS. 1 and 2.

FIG. 4 is a schematic representation of a machine to form the tube ofFIG.

FIG. 5 is a view similar to FIG. 2 of an alternative embodiment.

FIG. 6 is a view similar to FIG. 2 of two further embodiments.

DETAILED DESCRIPTION OF THE INVENTION

Referring therefore to FIG. 1, a form indicated by reference numeral 10has a cylindrical wall 12 formed from a helically wound strip 14.Abutting edges of the strip 14 are interconnected by a tongue and groovejoint generally indicated at 13 and seen in greater detail in FIGS. 2and 3. The tube 10 is formed to a nominal diameter D which typicallywill range between 6 and 12 inches. The wall 14 has a nominal thicknessindicated at b that is chosen so as to be sufficiently flexible toaccommodate the radius of curvature required whilst withstanding thepressure that may be exerted when used as a form. A nominal thickness of⅛″ is believed to be appropriate.

Referring therefore to FIG. 2, the strip 14 has a body 15 with lateraledges 17 and oppositely directed faces 19. Complementary formations inthe form of a groove 16 and a tongue 18 are formed on opposite lateraledges 17. The strip 14 is preferably made from a plastics material whichis flexible so as to be able to be formed into the smallest requireddiameter but also has sufficient strength to withstand the hydrostaticpressure of concrete placed within the tube.

As can be seen from FIG. 2, adjacent edges of the strip 14 areinter-engaged by the tongue 18 being inserted into the groove 16. Aswill be described in more detail below, the cross section of groove 16has a reentrant formation and the tongue 18 is of complementary crosssection with an enlarged end such that a snap fit is obtained betweenthe two to securely retain the tongue within the groove but allowing itto be removed subsequently. A locking key in the form of a strip 20 isinserted into a slot 22 formed in the tongue 18 to further secure thetongue within the groove.

Referring therefore to FIG. 3, the groove 16 has a part cylindrical base24 that terminates at shoulders 26. The shoulders 26 extend in oppositedirections from a channel 28 extending to an outer surface 30 of thestrip 14. A rabbet is formed at the outer edge of the strip 14 so as tointersect the channel 28 and form a step 32 of a height less than thethickness of the strip 14.

The opposite edge of the strip 14 is undercut as indicated at 34 toprovide a flange 36 that is complimentary to the step 32. The tongue 18projects from the flange 36 and has a profile complementary to that ofthe groove 16. The tongue 18 has a part cylindrical head 40 terminatingin abutment faces 42. A neck 44 of the tongue 18 connects the tongue tothe flange 36 and has a pair of opposed walls 46 that define a slot 22.

To define a cylindrical tube 10 as shown in FIG. 1, the strip 14 iswound in a helical form so that the tongue 18 is aligned with the groove16. The cylindrical head of the tongue permits it to be inserted intothe channel 28 such that the abutment faces 42 engage the underside ofthe shoulders 26 and securely hold the tongue within the groove. In thisposition, by virtue of the provision of the step 32 and the flange 36,adjacent passes of the strip are aligned presenting a continuous smoothsurface. The key 20 may then be inserted into the slot 22 to expand theneck 44 within the channel 28 and further secure the tongue 18 withinthe groove 16.

With a cylindrical tube defined, it may be used as a form with, forexample, concrete, to hold the concrete until it is solidified. Uponsetting of the concrete, the key 20 is removed and strip 14 may then beunwound by pulling the tongue 18 out of the groove 16. This will proceedin a smooth progressive manner along the length of the strip to releasethe tube from the outer surface of the cured concrete.

It will be apparent from the above description that the strip 14 may bestored in rolls of sufficient length provided to permit a tube of therequired diameter and length to be formed. The diameter through whichthe strip is wound may be varied to provide tubes of different length.

To facilitate the formation of the tube 10, a winding apparatus as shownschematically in FIG. 4 may be used.

Referring therefore to FIG. 4, a forming machine 50 has an unexpandablemandrill 52 about which the strip 14 may be rolled. The mandrill 52 ismounted upon a shaft 54 which in turn is rotatably mounted upon asupport 56. A spider assembly 58 is fixed to the shaft 54 adjacent thesupport 56 and carries four arms 60 that are pivotally connected to thespider 58. A slidable spider 62 is mounted on the opposite end of theshaft 54 and similarly carries arm 64. Support bars 66 extend betweenthe outer ends of the aims 64 to define the mandrill 52. The spiders 58,62 are mounted on splines provided on the shaft 54 so that they mayrotate their width. However, the slide at the spider 62 is axiallydisplaceable along the shaft to define the outer diameter of themandrill 52.

The shaft 54 is driven through a belt drive 66 from an electric motor 68that is mounted on the support 56. The support 56 also carries a niproller 70 that is mounted upon a shaft 72. The shaft 72 is rotatablymounted on the support 56 and driven through a belt drive 74 from themotor 68. The nip roller is adjustable relative to the shaft 54 so thatit may be positioned adjacent to but spaced from the bars 66.

To form a tube 10, strip 4 shown in ghosted outline of FIG. 4 is fed atan angle onto the mandrill 52 between the nip roller and the outersurface of the bars 66. The nip roller 70 progressively forces thetongue 1S into the groove 16 as the mandrill is rotated to provide acontinuous forming of the tube 10 that projects axially from themandrill. After the desired length of tube has been formed, the stripmay be cut and the ends of tube trimmed square for subsequent use.

Where a key is inserted into the slot 22, an additional roller 76 isspaced from the nip roller 70 and the key fed into the slot 60 andforced into the slot 22 by the action of the roller 76.

It will be appreciated that the formation of the tube 12 may beconducted at a building supply outlet or can be delivered as a strip onsite where the tube can then be formed of the required diameter.

Reinforcement of the tube 10 may be provided by forming multiple layerson the tube. Such an arrangement is shown in FIG. 5 where a first layerof the wall 12 is formed as described above. In this arrangement, thestrip 14 a is formed with a groove 16 a intermediate the lateral edgesof the strip 14 a. The groove receives a tongue 18 a projecting from theunderside of a further strip 14 b. The strip 14 b is formed with theinter-engaging formation at opposite lateral edges but has theadditional tongue 18 a for engagement with a radially inner wall.

A further embodiment is shown in FIG. 6 in which like reference numeralswill be denoted by like components with a prefix 1 for clarity.Referring therefore to FIG. 6, the strip 114 is formed with a grove 116a intermediate the lateral edges of the strip 114. The groove 116 a isarranged to receive a tongue carried on the underside of an additionalstrip arranged radially as shown with respect to FIG. 5. The laterallyouter edges of the strip 114 are formed with a groove 116 and tongue 118that are simple hook members and do not provide a re-entrant formation.The groove 116 and tongue 118 inhibits axial separation of adjacentpasses at the strip but radial locking of the strip is provided by theinter-engagement of the re-entrant intermediate groove 116 a and thecorresponding tongue carried by the adjacent layer.

It will also be observed in FIG. 6 that the strip 114 is formed withhollow cells 180 defined between a pair of webs 182, 184. The cells 180may be formed during extrusion of the strip in a conventional manner.The provision of the cells 180 decreases the weight of the strip whilstmaintaining the structural integrity.

As a further alternative as shown on the right hand side of FIG. 6, thestrip may be formed with a single web 182 with the groove 116 aupstanding from the web 182. Flanges 186 are provided intermediategrooves 116 a so as to provide a re-entrant channel on one side of theweb 182. The flanges provide the necessary radial stiffness but alsofacilitate the attachment of support brackets 190 that may be snappedinto the re-entrant channel at discrete locations. In the embodimentshown in FIG. 6, the bracket 190 is arranged to receive a standarddimensional lumber brace, typically a two by four, so that the brace maybe secured to the tube to assist in maintaining it in its desiredlocation during pouring of the concrete. The brackets 190 may beattached at a number of different locations about the circumference ofthe tube and at different axial positions along the tube.

It will be seen therefore that a simple yet effective tube is providedwhich may be assembled from strip to facilitate storage of the material.Assembly of the tube from the strip is relatively straightforward andpermits the tube to be made to the desired length and diameter to suitparticular circumstances. The tube may be formed with multiple layersand the strip may have different configurations to facilitatemanufacturer.

1. A concrete form having a tubular body formed from a flexile stripwound helically in successive passes to define a wall of said form,adjacent edges of said strip being releasably engaged with one anotherto inhibit axial separation of said strip.
 2. A concrete form accordingto claim 1 wherein said adjacent edges are inter-engaged by a grooveformed on one edge of said strip and a tongue foiled on an opposite edgeof said strip.
 3. A concrete form according to claim 2 wherein saidtongue and groove have complementary re-entrant formations to inhibitradial separation of said tongue from said groove.
 4. A form accordingto claim 2 wherein a locking spline is inserted into said tongue toinhibit axial separation of said tongue and said groove.
 5. A formaccording to claim 4 wherein said tongue and groove have complementaryre-entrant formations to inhibit radial separation of said tongue fromsaid groove.
 6. A form according to claim 1 wherein a groove is providedintermediate said edges to receive a tongue projecting from an adjacentoverlying strip.
 7. A form according to claim 1 wherein an open channelis provided on an external surface of said strip to receive a bracket.8. A form according to claim 1 wherein said strip is formed from aplastics material.
 9. A form according to claim 8 wherein said strip hashollow cells formed therein between external walls of said strip.
 10. Aform according to claim 9 wherein said tongue and groove havecomplementary re-entrant formations to inhibit separation of adjacentedges of said strip.
 11. A method of forming tubular form from a stripof material having tongue and a groove formed on one edge and a tongueformed on an opposite edge, said method comprising the steps ofhelically winding said strip to bring adjacent edges into abutment andengaging said tongue with said groove to inhibit axial separation ofadjacent edges.
 12. A method according to claim 11 including the step ofinserting a locking spline into said tongue.
 13. A method according toclaim 11 including the step of juxtaposing a pair of strips to provide apair of layers and inter-engaging said layers to inhibit radialseparation.
 14. A strip for use in forming a tubular form, said striphaving a body of flexible material, a tongue formed on one edge of saidbody, a groove on an opposite edge of said body, said tongue and groovehaving complementary cross sections to permit inter-engagement of saidtongue and groove to inhibit axial separation.
 15. A strip according toclaim 14 wherein said tongue and groove have complementary reentrantformations.
 16. A strip according to claim 14 wherein said tongue has aslot to receive a locking spline.
 17. A strip according to claim 16wherein said tongue and groove have complementary re-entrant formations.18. A strip according to claim 11 including an auxiliary groove formedintermediate said edges or one surface of said body.
 19. A stripaccording to claim 18 wherein said auxiliary groove has a re-entrantformation.
 20. A strip according to claim 11 including an auxiliarytongue projecting from said body intermediate said edges.
 21. A stripaccording to claim 20 wherein said auxiliary tongue has a re-entrantformation.